Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$103.51	13.789%	$117.783	$117.78	$117.80	$117.80
Purchase #2	$124.39	6.731%	$132.7627	$132.76	$132.75	$132.80
Purchase #3	$247.42	12.144%	$277.4667	$277.47	$277.45	$277.50
Purchase #4	$131.82	9.155%	$143.8881	$143.89	$143.90	$143.90
Purchase #5	$211.25	9.328%	$230.9554	$230.96	$230.95	$231.00
Purchase #6	$52.90	5.652%	$55.8899	$55.89	$55.90	$55.90
Purchase #7	$49.55	5.307%	$52.1796	$52.18	$52.20	$52.20
7 purchase totals =	$920.84		$1,010.9254	$1,010.93	$1,010.95	$1,011.10